On an extraordinarily high strength of a two-phase VT8-based titanium alloy heavy alloyed with zirconium

R.A. Gaisin, V.M. Imayev, E.R. Gaisina, R.A. Shaimardanov, R.M. Imayev


New two-phase VT8-based titanium alloy  and its mechanical properties are considered. Microstructure of the VT8-20Zr-0.1B alloy after multiple isothermal forging (a) subsequent quenching (b) and ageing (c) is shown on the figure. A novel two-phase titanium alloy based on VT8 having the composition VT8-20Zr-0.1B (Ti-6.5Al-3.3Mo-0.3Si) (wt. %) has been considered in the present paper. It has been established that modifying with boron leads to refinement of prior β grains and α/β colonies by a factor of about ten and alloying with zirconium results in some additional colony refinement. Alloying with 20 wt. % of zirconium leads to decreasing the α+β→β transformation temperature by about 100°C that along with refinement of the as-cast structure improved the hot workability of the alloy. After multidirectional hot forging in the α+β phase field (Т = 800°С) and hardening heat treatment the strength of the ВТ8-20Zr-0.1B alloy at 20-500°C was found to be higher by 30-40% as compared with that of the VT8 alloy after the same treatment while retaining similar ductility of the alloys. This allows one to characterize the VT8-20Zr-0.1B alloy as an ultrastrong titanium alloy. For the VT8-20Zr-0.1B alloy the following tensile properties have been attained: σUTS = 1560 MPa and δ = 4% at room temperature, σUTS = 1230 MPa and δ = 14% at Т = 500°С. The specific strength reached at Т=500°С (σUTS/ρ ≈ 248 MPa/g×cm-3) is the highest even obtained at this temperature for currently known titanium alloys. It was revealed that water quenching from the β phase field led to the martensitic β→α″ transformation with retained β phase and subsequent ageing resulted in formation of ultrafine lamellar structure with a nanosized lamellae thickness that promoted achieving significant strengthening.

References (13)

Metallography of Titanium Alloys. Ed. by N. F. Anoshkin. Moscow. Metallurgy (1980) 464 p. (in Russian) [Металлография титановых сплавов. Под ред. Н. Ф. Аношкина М. «Металлургия», (1980) 464 с.].
A. A. Il’in, B. A. Kolachev, I. S. Pol’kin. Titanium alloys. M. VILS-MATI. (2009) 519 p. (in Russian) [А. А. Ильин, Б. А. Колачев, И. С. Полькин. Титановые сплавы. М. ВИЛС-МАТИ. (2009) 519 с.].
C. Leyens, M. Peters, «Titanium and Titanium Alloys, Fundamentals and Applications». Weinheim, Germany (2003) 513 p.
A. I. Khorev. Technology of mechanical engineering. 6, 5 – 8 (2012) (in Russian) [А. И. Хорев. Технология машиностроения. 6, 5 – 8 (2012)].
R. Jing, S. X. Liang, C. Y. Liu, M. Z. Ma, X. Y. Zhang, R. P. Liu. Mater. Sci. Eng. A. 552, 295 – 300 (2012).
R. Jing, S. X. Liang, C. Y. Liu, M. Z. Ma, R. P. Liu. Mater. Sci. Eng. A. 559, 474 – 479 (2013).
J. Zhu, A. Kamiya, T. Yamada, W. Shi, K. Naganuma. Mater. Sci. Eng. A. 339, 53 – 62 (2003).
R. Srinivasan, D. Miracle, S. Tamirisakandala. Mater. Sci. Eng. A. 487, 541 – 551 (2008).
S. Roy, A. Sarkar, S. Suwas. Mater Sci Eng: A. 528, 449 – 458 (2010).
R. A. Gaisin, V. M. Imayev, R. M. Imayev, E. R. Gaisina. Letters on Materials. 5 (2), 124 – 128 (2015). (in Russian) [Р. А. Гайсин, В. М. Имаев, Р. М. Имаев, Э. Р. Гайсина. Письма о материалах. 5 (2), 124 – 128 (2015)].
V. M. Imayev, R. A. Gaisin, R. M. Imayev. Mater. Sci. Eng. A. 641, 71 – 83 (2015).
C. Lin, G. Yin, Y. Zhao, P. Ge, Z. Liu. Mater. Chem. Phys. 125, 411 – 417 (2011).
J. Soyama, M. Oehring,W. Limberg, T. Ebel, K. U. Kainer, F. Pyczak. Mater. Design. 84, 87 – 94 (2015).